Wis. Stat. § 944.20: Lewd and lascivious behavior.

(1) Whoever does any of the following is guilty of a Class A misdemeanor:

(a) Commits an indecent act of sexual gratification with another with knowledge that they are in the presence of others; or

(b) Publicly and indecently exposes genitals or pubic area.

(2) Subsection (1) does not apply to a mother’s breast-feeding of her child.